What Is Queue in Data Structure PDF?


Heather Bennett

In data structures, a queue is a linear data structure that follows the FIFO (First-In-First-Out) principle. It is an abstract concept similar to a queue of people waiting in line, where the first person who joined the line is served first. Queues are widely used in computer science and programming to efficiently manage and process data.

Understanding Queue

A queue can be visualized as a collection of elements arranged in a specific order. The elements are added at one end, known as the rear, and removed from the other end, known as the front. This order ensures that the element that has been in the queue for the longest time is always at the front and will be processed first.

Operations on Queue

A queue typically supports two main operations:

  • Enqueue: Adding an element to the rear of the queue.
  • Dequeue: Removing an element from the front of the queue.

In addition to these fundamental operations, queues also often provide other auxiliary operations such as:

  • Peek: Viewing (without removing) the frontmost element of the queue.
  • Size: Determining the number of elements currently in the queue.
  • Empty: Checking if the queue is empty or not.

The Implementation of Queue

A queue can be implemented using various data structures such as arrays, linked lists, or even stacks. Each implementation has its own advantages and disadvantages based on factors like performance, memory utilization, and ease of implementation.

Array-based Queue

An array-based queue uses a fixed-sized array to store the elements. The rear and front are represented as indices pointing to the last element and the first element, respectively.

When an element is enqueued, it is added at the rear index, and when an element is dequeued, it is removed from the front index. However, this implementation has a limitation of fixed size.

Linked List-based Queue

A linked list-based queue uses a doubly linked list as its underlying data structure. Each node in the linked list contains an element along with references to the next and previous nodes.

The front and rear are represented by pointers to the first and last nodes of the linked list. This implementation allows for dynamic resizing, making it more flexible than an array-based queue.

Applications of Queue

Queues find applications in various domains such as:

  • Operating Systems: Queues are used for process scheduling and managing system resources.
  • Data Processing: Queues facilitate data buffering and handling large datasets efficiently.
  • Networks: Queues help manage network traffic by prioritizing packets for transmission.
  • Synchronization: Queues enable synchronization between different threads or processes.

Example: Printing Documents

An example scenario where queues are commonly used is printing multiple documents on a printer. The print jobs are added to a queue in the order they arrive. The printer processes each job one by one in a FIFO manner until all documents have been printed.

In conclusion, a queue in data structure PDF represents a linear collection of elements that follows the FIFO principle. It is widely used in various applications and can be implemented using different data structures. Understanding queues and their operations is essential for efficient data processing and management.

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